Synthesis,crystal growth and characterization of Tl3BX4-compounds (B = V,Nb, Ta; X = S,Se)

Single crystals of Tl₃BX₄-compounds (B = V, Nb, Ta; X = S, Se) were grown by the Bridgman-Stockbarger technique. The compounds were synthesized from the high-purity elements. The melting points were determined by differential thermal analysis. Tl₃VS₄, Tl₃TaS₄ and Tl₃TaSe₄ yielded single crystals up to 10 cm³. The other compounds show single crystalline pieces up to 1 cm³. Infrared photographs and electron microprobe analyses revealed inclusions of TlS in the sulfur compounds, in Tl₃VSe₄ and Tl₃NbSe₄ inclusions of TlSe and in Tl₃TaSe₄ small amounts of Ta.     

Synthesis and characterization of MAgSe4 (M=Rb, Cs)

Syntheses of the title compounds were achieved from supercritical amines. The single crystal X-ray characterization of both MAgSe₄ (M=Rb, Cs) members indicates that they are isostructural. The structure is built from five membered AgSe₄ rings that are stitched together through tetrahedrally coordinated Ag(I) ions to form one dimensional chains running parallel to the a-axis. These chains are separated from each other by the alkali metal cations. Crystal data: orthorhombic, P2₁2₁2₁, Z = 4. RbAgSe₄: a = 5.809(2), b = 8.927(3), c = 13.435(4) Å, U = 698.2(4) ų, and D _c = 4.851 g/cm³. CsAgSe₄: a = 5.855(2), b = 9.090(3), c = 13.885(4) Å, U = 739.0(4) ų, and D _c = 5.003 g/cm³. The anionic chain found in the title compounds has been observed previously, and comparisons among these phases show that the silver ion coordination in the chain varies as a function of cation size. Both the title compounds are valence precise and optical diffuse reflectance studies show that they are semiconductors with moderately large band gaps.     

Preparation and some properties of thallium orthothioarsenate single crystals

Growing of large (Ø 25–30 mm, L = 50–60 mm) optically homogenous single crystals of Tl₃AsS₄ using the Bridgman-Stockbarger method is described. Tl₃AsS₄ is orthorhombic (Pnma), a = 8.85 ± 0.03, b = 10.86 ± 0.03, c = 9.18 ± 0.03 Å; z = 4; ϱ_x = 6.15 g · cm⁻³; ϱ_p = 6.15 ± 0,03 g · cm⁻³, T_m = 424 ± 3°C, Moh's hardness = 3, microhardness and ultrasonics velocity along x, y, z are 65–85 kg · mm⁻² and 2.16 – 2.37 · 10⁵ cm · sec⁻¹, respectively. The crystals possess perfect cleavage plane (010). Their transparency range is 0.6–12 microns. – Unsuccessful attempts to obtain Tl₃AsS₄ and its alloys in the vitreous state were taken. The possibilities of glass formation and boundaries of the vitreous region in the system Tl–As–S based on the characteristic features of the melt forming structural units are analyzed.     

Thermal dehydration of the double salts K2Be(XO4)2·2H2O (X = S,Se)

The thermal dehydration of the title compounds was studied by TG, DTA and DSC methods and the enthalpies of dehydration were calculated (87.6 kJ mol^–1 and 167.5 kJ mol^–1 for the sulfate and selenate compound, respectively). The larger value of ΔH_deh of K₂Be(SeO₄)₂·2H₂O is due to the stronger hydrogen bonds formed in the selenate as compared to those formed in the respective sulfate owing to the stronger proton acceptor capabilities of the SeO₄^2– ions. The enthalpies of formation (ΔH_f⁰) of the dihydrates are also calculated from the DSC measurements (– 4467.4 kJ mol^–1 and – 3447.1 kJ mol^–1 for the sulfate and selenate compound, respectively). The anhydrous double salt, K₂Be(SO₄)₂, forms tetragonal crystals with lattice parameters: a = 7.232(2) Å; c = 14.168(2) Å; V = 741.0 ų, while the anhydrous salt, K₂Be(SeO₄)₂, forms monoclinic crystals with lattice parameters: a = 9.217(3) Å; b = 10.645(3) Å; c = 8.989(2) Å; β = 108.52(4)°; V = 836.2 ų. Vibrational spectra (infrared and Raman) of both the dihydrates and the anhydrous compounds are also presented and discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

4,5-Bis(benzylthio)-1,3-dithiole-2-thione compounds: crystal structures of [(p-XC6H4CH2)(p-XC6H4CH2)dmit: X=Y=OMe; X=Y=NO2; and X=OMe, Y=NO2]

4,5-Bis(benzylthio)-1,3-dithiole-2-thiones, [(p-XC₆H₄CH₂)(p-XC₆H₄CH₂)dmit: X=Y=OMe (2); X=OMe, Y=NO₂ (3); and X=NO₂] (4)] have been prepared from benzyl chlorides and [NEt₄]₂[Zn(dmit)₂]. Isostructural compounds, 2 and 3, crystallize in the triclinic space group (Z = 2) with a = 5.2920(10), b = 10.537(2), c = 18.961(4) Å, = 102.79(3), = 96.33(3), = 98.67(3)° for 2; a = 5.292(8), b = 10.528(12), c = 19.01(2) Å, = 102.74(9), = 96.26(11), = 98.56(11)° for 3. Compound 4 also crystallizes in the space group (Z = 4), with a = 9.296(8), b = 13.993(18), c = 16.186(4) Å, = 106.68(3), = 89.63(3), = 99.38(6)°. Molecular differences between 2 and 3, on one hand, and 4, on the other, arise in the disposition of the aryl rings relative to the dmit group. Short S---S contacts in 2 of 3.320(2) Å [S3---S3 ⁱ (symmetry operation: i: –x + 1, –y + 1, –z)] and in 3 of 3.314(5) Å [S3---S3 ⁱ (symmetry operation: i: –x + 1, –y, –z + 1)] link molecules into pairs. In 4, an S5A---S2B contact of 3.516(5) Å links two independent molecules, A and B, into bimolecular units, which are further connected into chains by S2A---S5B ⁱ contacts (symmetry operation: i: x, y, z – 1) at 3.569(5) Å. C–H---O hydrogen bonds are also present in 3 and 4.     

The crystal structures of NaAlR4, R=methyl,ethyl, and n-propyl

The crystal structures of the title compounds have been determined from diffractometer data and refined by full-matrix least squares. NaAlMe₄ is orthorhombic,Cmcm,a=9.234(3),b=9.221(3),c=8.303(2) Å,Z=4,D _c=1.03 g cm^–3,R=0.029 for 278 data. NaAlEt₄ is monoclinic,P2₁/c (No. 14),a=13.900(2),b=13.207(2),c=14.443(1) Å,=117.43(1)°,Z=8,D _c=0.94 g cm^–3,R=0.056 for 2747 data. NaAl(n-Pr)₄ is monoclinic,C2/c,a=9.802(5),b=15.336(4),c=21.611(10) A,=98.34(4)°,Z=8,D _c=0.92 g cm^–3,R=0.072 for 899 data. Coordination of Al is essentially tetrahedral in all structures, and closest contacts to Na⁺ involve-carbon atoms of alkyl groups.     

Synthesis and structures of Na4P2Se6, Cs3PSe4, and Rb4P2Se9

Na₄P₂Se₆ (1) crystallizes in the orthorhombic space group Cmca (No. 64) with a = 11.836(3) ?, b = 13.311(4) ?, c = 8.061(2) ?, V = 1270.0(6) ?³, Z = 4, and, D _c = 3.283 g/cm³. Na₄P₂Se₆ belongs to the family of compounds with the general formula where A = Na⁺ and Q = Se²⁻. The crystal structure consists of isolated ethane-like P₂Se anions surrounded by Na⁺ cations. Cs₃PSe₄ (2) crystallizes in the orthorhombic space group Pnma (No. 62) with a = 10.0146(9) ?, b = 11.9899(10) ?, c = 9.9286(9) ?, V = 1192.17(18) ?3, Z = 4, and, Dc = 4.154 g/cm³. Cs₃PSe₄ belongs to the family of compounds with the general formula [(A^{+ x} ) _{z / x} (P ^v Q₄)^{− z} ] where A = Cs⁺ and Q = Se²⁻. The crystal structure consists of isolated methane-like PSe anions surrounded by Cs⁺ cations. Rb₄P₂Se₉ (3) crystallizes in the monoclinic space group C2/c (No. 15), a = 9.725(2) ?, b = 10.468(3) ?, c = 19.155(5) ?, β = 93.627(5)°, V = 1946.1(8) ?³, Z = 4, D _c = 3.804 g/cm³. Rb₄P₂Se₉ belongs to the family of compounds with the general formula [(A^{+ x} )_{(2 z −2)/ x} (Q₃PQ′—Q″—Q′PQ₃)^{−(2 z −2)}] where A = Cs⁺ and Q = Se²⁻, Q′ = Se¹⁻, Q″ = Se⁰. The crystal structure consists of isolated P₂Se anions surrounded by Rb⁺ cations.     

The double phosphates MIMIIPO4 (MI – Na,K; MII – Mg,Mn, Co,Ni, Zn) – synthesis from chloride melts and characterization

The particularities of the chemical interaction in systems M^IPO₃‐M^IIO(or Mn₂O₃)‐M^ICl (M^I – Na, K; M^II – Mg, Co, Ni, Zn) have been investigated at the temperature 1073 K and molar ratios P/M^x = 1 or 2 and M^ICl/(M^IPO₃ + M^IIO(or Mn₂O₃)) = 30. The conditions of formation of complex phosphates M^ІM^IIPO₄ and Na₄Ni₃(PO₄)₂P₂O₇ have been found. Influences of the nature of alkali and bivalent metals on the products composition were discussed. The advantages of chloride melts using (synthesis time reduction and temperature reducing) for preparing of complex phosphates were shown. The synthesized compounds have been characterized using the powder X‐ray diffraction, Fourier transform infrared and diffuse reflectance spectroscopies.     

Crystal structure of the gold(I) complex [Au(tfp)Cl] with tfp = (C<Subscript>4</Subscript>H<Subscript>3</Subscript>O)<Subscript>3</Subscript>P

The Au(I) complex [Au(tfp)Cl] with tfp = (C₄H₃O)₃P has been prepared and characterised. It crystallises in the monoclinic P2₁/n space group with z = 4, a = 9.837(3), b = 12.684(4), c = 11.103(5)Å, = 91.58(2)° and V = 1384.8(2)ų. The structure of the complex consists of molecules connected in head-to-tail dimers by a metal-halogen contact as generally found in analogus complexes of lighter coinage metals. The typical feature of halogen gold compounds, the Au–Au interaction, seems prevented by the bulk of the tfp ligand.     

Imidazolium based ionic liquid crystals: structure,photophysical and thermal behaviour of [Cnmim]Br·xH2O (n = 12, 14; x=0, 1)

The long chain imidazolium halides [C_nmim]Br·xH₂O (n = 10, 12; x = 0, 1) have been synthesized and their structural and thermal behaviour together with their photophysical properties characterized. X‐ray structure analyses of the monohydrates ([C₁₂mim]Br·H₂O: triclinic, P1, no. 2, Z = 2, Pearson code aP112, a = 550.0(5) pm, b = 779.4(5) pm, c = 2296.1(5) pm, α = 81.89(5)°, β = 83.76(5)°, γ = 78.102(5)°, 3523 unique reflections with I_o > 2σ(I_o), R₁ = 0.0263, wR₂ = 0.0652, GooF = 1.037, T = 263(2) K; [C₁₄mim]Br•H₂O: triclinic, P1, no. 2, Z = 12, Pearson code aP11, a = 549.86(8) pm, 782.09(13) pm, c = 2511.3(4) pm, α = 94.86(2)°, β = 94.39(2)°, γ = 101.83(2)°, 2063 unique reflections with I_o > 2σ(I_o), R₁ = 0.0429, wR₂ = 0.0690, GooF = 0.770, T = 293(2) K) show for both compounds similar bilayered structures. Sheets composed of hydrophilic structure regions constituted by positively charged imidazolium head groups, bromide anions and hydrogen bonded water alternate with hydrophobic areas formed by interdigitated long alkyl chains belonging to imidazolium cations with different orientation. Combined differential scanning calorimetry and polarizing optical microscopy shows that the monohydrates as well as the anhydrous imidazolium salts are thermotropic liquid crystals which adopt smectic mesophases. The mesophase region is larger in case of the monohydrates when compared to the anhydrous compounds indicating that water obviously stabilizes the mesophase. All compounds show an intense whitish photoluminescence with short lived (¹π←¹π*) and long lived (¹π←³π*) transitions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature and excitation intensity tuned photoluminescence in Tl4GaIn3S8 layered single crystals

Photoluminescence spectra of Tl₄GaIn₃S₈ layered crystals grown by Bridgman method have been studied in the wavelength region of 500–780 nm and in the temperature range of 26–130 K with extrinsic excitation source (λ_exc = 532 nm), and at T = 26 K with intrinsic excitation source (λ_exc = 406 nm). Three emission bands A, B and C centered at 514 nm (2.41 eV), 588 nm (2.11 eV) and 686 nm (1.81 eV), respectively, were observed for extrinsic excitation process. Variations in emission spectra have been studied as a function of excitation laser intensity in the 0.9‐183.0 mW cm^–2 range for extrinsic excitation at T = 26 and 50 K. Radiative transitions from the donor levels located at 0.03 and 0.01 eV below the bottom of the conduction band to the acceptor levels located at 0.81 and 0.19 eV above the top of the valence band were proposed to be responsible for the observed A‐ and C‐bands. The anomalous temperature dependence of the B‐band peak energy was explained by configurational coordinate model. From X‐ray powder diffraction and energy dispersive spectroscopic analysis, the monoclinic unit cell parameters and compositional parameters of Tl₄GaIn₃S₈ crystals were determined, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical Phonons and Chemical Bonding in TlSbS2, TlSbSe2, and Tl3SbS3 Crystals

The optical phonons at k = 0 of TlSbS₂, TlSbSe₂, and Tl₃SbS₃ have been investigated by infrared reflectivity measurements from 50 to 4000 cm⁻¹ at 300 K. The factor group analysis of vibrational modes of TlSbS₂ and Tl₃SbS₃ crystal lattices has been made. The dielectric constant dispersion for E ‖ a and E ‖ b has been determined by classical dispersion relations. The Szigeti effective charges, the Born dynamic effective charge, and the Tl, Sb, S (Se) relative ion charges were calculated in dependence on the polarization of the incident light.     

Ionicity of the chemical bond in Tl3XS4 compounds

Levine's extension of the Phillips-Van Vechten's dielectric theory to multibond crystals containing transition metals is used for estimating the bond ionicities in Tl₃XS₄ compounds (X = V, Nb, Ta).     

Crystal Structure of a New Quinternary Oxide: NaTl<Subscript>3</Subscript>Cu<Subscript>4</Subscript>Te<Subscript>2</Subscript>O<Subscript>12</Subscript>

Abstract  

A new quinternary oxide, NaTl₃Cu₄Te₂O₁₂, has been synthesized and characterized by single crystal X-ray diffraction. The reported material was synthesized by hydrothermal techniques using TlNO₃, CuO, TeO₂, and NaOH as reagents. The material exhibits a two-dimensional layered structure consisting of edge-shared CuO₆ and TeO₆ polyhedra separated by Na⁺ and Tl⁺ cations. NaTl₃Cu₄Te₂O₁₂ crystallizes in space group C2/m with a = 12.9800(17) ?, b = 9.3455(12) ?, c = 5.2335(7) ?, β = 104.276(2)°, V = 615.24(14) ?³, and Z = 2.     

Barite-type Ba(BeF4)x(SO4)1?x (x = 1 and ≈0.5)

Barite-type α-BaBeF₄ (a = 8.8594(3), b =5.3265(2), c = 7.0493(2) Å, Pnma (No. 62)) and Ba(BeF₄)_0.535(7)(SO₄)_0.465(7) (a = 8.8657(2), b = 5.3902(2), c = 7.1007(2) Å, Pnma (No. 62)) were prepared by precipitation from aqueous solutions and their structures refined from laboratory X-ray powder diffraction data. In the case of α-BaBeF₄ it was possible to identify the light atom Be on a difference Fourier map and to refine its positional parameters in the presence of a heavy atom (Ba). Both phases contain almost ideal isolated BX₄²⁻ tetrahedra (B = Be, Be/S and X = F, F/O) together with Ba, that is 12-fold coordinated by X. The plausibility of the resulting structures was proved with the help of the bond valence model. For both compounds no phase transitions were found up to 550^∘C.     

Crystal structure of 2‐(2'‐hydroxyphenyl)‐6‐tributylstannyl‐4‐(3H )‐quinazolinone and 2‐(2'‐hydroxyphenyl)‐6‐iodo‐4‐(3H)‐quinazolinone

The structures of the title compounds C₂₆H₃₇N₂O₂Sn ( I ) and C₁₄H₉IN₂O₂ ( II ) were determined by single‐crystal X‐ray diffraction technique. Compound I crystallizes in the triclinic space group P1 with a = 9.560(3) Å, b = 16.899(6) Å, c = 17.872(5) Å, α = 65.957(7)°, β = 83.603(5)°, γ ( = 75.242(5)°, V = 2549.8(13) ų, Z = 4, and D =1.374 g/cm³. The compound consists of a quinazolinone ring with phenol and tributylstannyl moieties. Compound II crystallizes in the monoclinic space group P2₁/c with a = 7.6454(12) Å, b = 5.9270(9) Å, c = 27.975(4) Å; α = 90°, β = 95.081(3)°, γ = 90°, V = 1262.7(3) ų, Z = 4, and D = 1.915 g/cm³. The compound consists of a quinazolinone ring with phenol and iodine substituents. For both I and II , the short intramolecular O–H…N and two long intermolecular N–H…O hydrogen bonds are highly effective in holding the molecular system in a stable state. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature‐tuned band gap energy and oscillator parameters of Tl2InGaSe4 semiconducting layered single crystals

The optical properties of Tl₂InGaSe₄ layered single crystals have been studied through the transmission and reflection measurements in the wavelength range of 500‐1100 nm. The analysis of room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 1.86 and 2.05 eV, respectively. Transmission measurements carried out in the temperature range of 10‐300 K revealed that the rate of change of the indirect band gap with temperature is γ = – 4.4 × 10^‐4 eV/K. The absolute zero value of the band gap energy was obtained as E_gi(0) = 1.95 eV. The dispersion of the refractive index is discussed in terms of the single oscillator model. The refractive index dispersion parameters: oscillator wavelength and strength were found to be 2.53 × 10^–7 m and 9.64 × 10¹³ m^–2, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Infrared vibrational Modes in Tl3SbS3, Tl3AsS3, and Tl3AsSe3 crystals

Reflectivity spectra of Tl₃SbS₃, Tl₃AsS₃, and Tl₃AsSe₃ crystals have been investigated in the wave number range 50–600 cm⁻¹ for the polarizations E∥c and E⟂c. The fundamental phonon parameters, the limiting dielectric constants ϵ_∞ and ϵ_S and the reflectivity spectra contours have been calculated by using classical dispersion relations for both E∥c and E⟂c configurations. The Szigeti effective charges and the relative ion charges of As, Tl, Sb, Se, S anions and cations have been calculated in dependence on the incident light polarization.     

Synthesis and structures of two chiral bis(pyrazolyl)borate complexes, [{H<Subscript>2</Subscript>B(4-Mepz)(3,5-Me<Subscript>2</Subscript>pz)}<Subscript>2</Subscript>M], M = Co,Zn

The title compounds are chiral and have similar molecular geometries. The Co complex crystallizes in space group P2₁/c with a = 8.475(4) Å, b = 7.706(8) Å, c = 35.778(9) Å, = 95.779(18) and Z = 4, while the Zn complex crystallizes in space group P2₁/n with a = 8.353(3) Å, b = 20.768(4) Å, c = 13.818(3) Å, = 100.96(2) and Z = 4. The metal atoms are tetrahedrally coordinated to two bidentate ligands with M–N distances in the ranges 1.985(2)–2.018(2) Å (Co) and 1.985(2)–2.008(2) Å (Zn), and N–M–N angles in the ranges 96.07(7)–128.23(7) (Co) and 98.50(8)–125.63(8) (Zn). No agostic bonds are formed. The molecules display C₁ symmetry; geometric considerations indicate that the formation of the other two possible conformers, with C₂ symmetry, is sterically less favorable.     

Thermoelectric properties of Tl‐doped Bi2Se3 single crystals

The single crystals of the ternary system based on Bi_2‐xTl_xSe₃ (nominaly x = 0.0‐0.1) were prepared using the Bridgman technique. Samples with varying content of Tl were characterized by the measurement of lattice parameters, electrical conductivity σ_⊥c , Hall coefficient R_H (B∥c), and Seebeck coefficient S (ΔT ⊥c). The measurements indicate that by incorporating Tl in Bi₂Se₃ one lowers the concentration of free electrons and enhances their mobility. This effect is explained in terms of the point defects in the crystal lattice – formation of substitutional defects thallium on the site of bismuth Tl_Bi and the decrease of concentration of selenium vacancies V_Se⁺². We also discuss the temperature dependence of the power factor σS² of the samples. Upon the thallium doping we observe a significant increase of the power factor compare to the parental Bi₂Se₃. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)